Wireless devices, which transfer data e.g. by means of radio, are increasingly used in all possible fields of everyday life. In industry and medicine also, the conventional data transfer by means of cables is increasingly being replaced by wireless techniques.
In industry and medicine, the increasing number of radio participants, e.g. including Bluetooth devices, typically transmit over a limited range but can also disrupt each other when operated concurrently. It is therefore desirable to prevent these devices from transmitting when this is not applicable. Mechanical contacts which are activated e.g. via a plug connector and prevent transmission by the devices are known for this purpose. However, these plug connectors can easily be lost or not plugged in due to forgetfulness.
A radio solution for transferring data is suitable in connection with magnetic resonance techniques, in particular, since electrical data lines are disrupted by the electromagnetic fields which exist in magnetic resonance devices, and can also themselves disrupt the recordings. The magnetic resonance technique (the abbreviation MR represents magnetic resonance in the following) is a known technique by means of which images of the interior of an examination object can be generated. Expressed simply, for this purpose, the examination object is positioned in an MR device in a comparatively strong static homogenous primary magnetic field (field strengths of 0.2 to 7 Tesla and higher), such that its nuclear spins are aligned along the primary magnetic field. For the purpose of triggering nuclear spin resonances, high-frequency excitation pulses are beamed into the examination object, the nuclear spin resonances are measured and MR images are reconstructed on the basis of these. For location coding of the measured data, rapidly switched magnetic gradient fields are superimposed on the primary magnetic field.
A mobile radio transmission unit for transferring physiological data is disclosed in DE 100 47 365 B4 (corresponds to U.S. Pat. No. 6,711,434). This document discloses a physiological sensor system which is designed in such a way that it can record measurement signals, in particular in a magnetic resonance device. However, the operation of this physiological sensor system in connection with an MR device presents particular requirements, since the strong magnetic fields and electromagnetic alternating fields of the MR device influence magnetic and electrically conductive objects by e.g. inducing currents and/or opposing fields or by pulling magnetic objects towards the magnets of the MR device. As a result, in particular the operation of electrical units can be disrupted and e.g. lead to false results.
One possibility for avoiding such undesired effects is to equip the affected objects with a screen against the fields of the MR device. In this way, devices having an electronic system can also be operated without disruption within the electromagnetic fields of an MR device.
Another possibility is to ensure that objects which can be affected are kept at an adequate distance from the MR device. This provides a solution in a simple manner, since the magnetic field decreases rapidly as the distance from the MR device increases.
For this purpose, a magnetic field detection system for the protection of connected electronic devices is disclosed in DE 196 26 596 A1 (corresponds to U.S. Pat. No. 5,629,622 A), for example, and emits warning signals when the connected electrical device comes too close to an MR device.
Such a solution is not viable in every case, however, since exposing certain electronic devices or units to strong magnetic fields is not always avoidable or might even be necessary.